1. Field of the Invention
This invention relates to a fixing device for electrophotographic duplicating machines, and more particularly to an offset preventive device for an image fixer used in such machines.
2. Discussion of the Prior Art
It is well known, in electrophotographic copying machines to transfer a powder image onto a copy medium from a xerographic plate and heat it in a heat-contact fixer to a viscous state so that the image may be fixed to the copy medium. However, there is a tendency, when using heat rollers, for a portion of the image disposed on the copy medium to deposit on the surface of the contact heat roller. As a result, the viscous image portions, which have been deposited from the copy medium in the preceding revolution of the heat roller, are partially transferred to the copy medium again on the succeeding revolution of the heat roller. At the same time a fresh viscous image portion is transferred to the heat roller as in the preceding revolution thereof. This phenomenon is generally known as "offset" and, in order to minimize it, it is known to coat the surfaces of the heat roller with an offset preventive material such as a fluorine-containing resin and to provide an offset preventive solution feed device for supplying offset preventive solution such as a silicon oil to the offset preventive material of the heat roller.
However, the offset preventive solution feed device must both feed the offset preventive solution and, at the same time, remove depositions of viscous developing agent from the heat roller. However, the viscous developing agent which has been removed from the heat roller by the offset preventive solution feed member is accumulated thereon during repeated operations, thereby clogging the heat resistant fiber material of the offset preventive solution feed member to such a degree as to make it very difficult to supply the desired offset preventive solution. The viscous developing agent which accumulates on the offset preventive solution feed member tends to deposit again on the heat roller, thus causing further problems.